Process for making aligned carbon nanotubes

ABSTRACT

A process for preparing a patterned layer of aligned carbon nanotubes on a substrate including: applying a pattern of polymeric material to the surface of a substrate capable of supporting nanotube growth using a soft-lithographic technique; subjecting said polymeric material to carbonization to form a patterned layer of carbonized polymer on the surface of the substrate; synthesising a layer of aligned carbon nanotubes on regions of said substrate to which carbonized polymer is not attached to provide a patterned layer of aligned carbon nanotubes on said substrate.

BACKGROUND OF THE INVENTION

This is a National Stage entry under 35 U.S.C. § 371 of Application No.PCT/AU00/001180 filed Sep. 22, 2000, and the complete disclosure ofwhich is incorporated into this application by reference.

This invention relates to carbon nanotube materials and processes fortheir preparation. In particular the invention relates to patternedaligned carbon nanotubes and to processes for their preparation whichinvolve the use of a soft-lithographic technique. The invention alsorelates to the construction of various electronic and photonic devicesfrom such materials for practical applications in many area including aselectron field emitters, artificial actuators, chemical sensors, gasstorages, molecular filtration membranes, energy absorbing materials,molecular transistors and other opto electronic devices.

SUMMARY OF THE INVENTION

Soft-lithography has recently become a very promising technique formicro-/nano-structuring a wide range of materials (see, for example:Xia, Y.; Whitesides, G. M. Annu. Rev. Mater. Sci. 1988, 28, 153).Various strategies, including micro-contact prining (μCP), mechanicalscraping, and micro-molding, have been developed for nanoscalepatterning that otherwise is difficult by photolithographic techniques(see, for example: Dai, L. J. Macromol. Sci., Rev. Macromol. Chem. Phys.1999, 39, 273, and references cited therein). In particular,micro-contact printing (μCP) has been demonstrated to be a veryconvenient pattering technique for generating self-assembled monolayer(SAM) patterns of certain molecular “inks” (e.g. alkanethiol,alkylsiloxane) on an appropriate substrate surface (e.g. gold, silver,copper, aluminium, and silicon dioxide surfaces) using an elastomericstamp (typically, a polydimethylsiloxane (PDMS) stamp) for aregion-specific transfer of the SAM material. On the other hand, thesolvent-assisted micromolding (SAMIM) technique allows pattern formationthrough confined solvent evaporation from a thin layer of polymersolution sandwiched between a PDMS elastomer mold and substrate surface.However, it has been a major challenge for researchers to find ways tocontrol the arrangement of carbon nanotubes.

Carbon nanotubes usually have a diameter in the order of tens ofangstroms and the length of up to several micrometers. These elongatednanotubes consist of carbon hexagons arranged in a concentric mannerwith both ends of the tubes normally capped by pentagon-containing,fullerene-like structures. They can behave as a semiconductor or metaldepending on their diameter and helicity of the arrangement of graphiticrings in the walls, and dissimilar carbon nanotubes may be joinedtogether allowing the formation of molecular wires with interestingelectrical, magnetic, nonlinear optical, thermal and mechanicalproperties. These unusual properties have led to diverse potentialapplications for carbon nanotubes in material science andnanotechnology. Indeed, carbon nanotubes have been proposed as newmaterials for electron field emitters in panel displays,single-molecular transistors, scanning probe microscope tips, gas andelectrochemical energy storages, catalyst and proteins/DNA supports,molecular-filtration membranes, and energy-absorbing materials (see, forexample: M. Dresselhaus, et al., Phys. World, January, 33, 1998; P. M.Ajayan, and T. W. Ebbesen, Rep. Prog. Phys., 60, 1027, 1997; R. Dagani,C&E News, Jan. 11, 31, 1999).

For most of the above applications, it is highly desirable to preparealigned carbon nanotubes so that the properties of individual nanotubescan be easily assessed and they can be incorporated effectively intodevices. Carbon nanotubes synthesised by most of the common techniques,such as arc discharge, often exist in a randomly entangled state.However, aligned carbon nanotubes have recently been prepared either bypost-synthesis manipulation or by synthesis-induced alignment (see, forexample: S. Huang, L. Dai and A. W. H. Mau H, J. Mater. Chem. (1999), 9,1221 and references cited therein).

The number of techniques which have been reported for the patternformation of aligned carbon nanotubes is very limited (S. Fan, M. G.Chapline, N. R. Franklin, T. W. Tombler, A. M. Cassell, and H. Dai,Science, 283, 512, 1999; S. Huang, L. Dai, and A. W. H. Mau, J. Phys,Chem., 103 issue 21, 4223-4227), and the achievable resolutions of thenanotube patterns was, at the best, at several micrometer scale in thesecases.

It has now been found that pattern formation of perpendicularly alignedcarbon nanotubes with resolutions up to a sub-micrometer scale can beachieved using a novel soft-lithographic technique.

According to a first aspect, the present invention provides a processfor preparing a patterned layer of aligned carbon nanotubes on asubstrate including:

-   -   applying a pattern of polymeric material to the surface of a        substrate capable of supporting nanotube growth using a        soft-lithographic technique,    -   subjecting said polymeric material to carbonization to form a        patterned layer of carbonized polymer on the surface of the        substrate,    -   synthesising a layer of aligned carbon nanotubes on regions of        said substrate to which carbonised polymer is not attached to        provide a patterned layer of aligned carbon nanotubes on said        substrate.

The polymeric material may be any polymer capable of being applied tothe substrate surface in the form of a pattern using a soft-lithographictechnique, and which is capable of undergoing carbonization. The patternof carbonized polymer so formed should correspond to the pattern ofpolymer applied to the substrate using the soft-lithographic technique.Examples of suitable polymers include, but are not limited to,photoresist or photoresponsive materials, such as diazonaphtoquinone(DNQ)-based photo resists (e.g. cresol novolak resin from Shipley,Ozatec PK 14 from Hoechst), as well as other possible polymersincluding, inter alia, epoxy resins, PEO, polyanilines, polymethylmethacrylate, polystyrenes, polydienes and plasma polymers derived fromsaturated or unsaturated alcohols, ketones, aldehydes, amines or amides.Preferably the polymer is a diazonaphaquinone (DNQ)-modified cresolnovolak photoresist.

The substrate to which the polymer patterned layer is applied can be anysubstrate which is capable of withstanding the pyrolysis conditionsemployed, and capable of supporting aligned carbon nanotube growth.Examples of suitable substrates include all types of glass that providesufficient thermal stability according to the synthesis temperatureapplied, such as quartz glass, as well as alumina, graphite, mica,mesaporous silica, silicon wafer, nanoporous alumina or ceramic plates.Preferably the substrate is glass, in particular, quartz glass orsilicon wafer. The substrate may also include a coating of a materialwhich is capable of supporting carbon nanotube growth under theconditions employed. The coating may be of any metal, metal oxide, metalalloy or compound thereof, which may have conducting or semiconductingproperties. Examples of suitable metals include Au, Pt, Cu, Cr, Ni, Fe,Co and Pd. Examples of suitable compounds are metaloxides, metalcarbides, metal nitrides, metal sulfides and metal borides. Examples ofsuitable metal oxides include indium tin oxide (ITO), Al₂O₃, TiO₂ andMgO. Examples of semiconducting materials include gallium arsenide,aluminium arsenide, aluminium sulphide and gallium sulphide.

The patterning of the aligned carbon nanotubes is achieved by creating aregion on the substrate which is incapable of supporting nanotubegrowth. The pattern is created on the substrate using an appropriatesoft-lithographic technique. Examples of suitable soft-lithographictechniques include micro-contact printing (μCP) and micro-molding.

In one embodiment the micro-contact printing process involves theregion-specific transfer of self-assembling monolayers (SAMs) of amolecular “ink”, such as alkylsiloxane, onto a suitable substrate,followed by subsequent adsorption of the polymer in the SAM-freeregions. The transfer of the self-assembling monolayer may be achievedusing an appropriate stamp, such as a polydimethylsiloxane (PDMS) stamp.Other processes which involve region-specific transfer of a materialwhich alters the hydrophobicity or hydrophilicity of the substratesurface may also be used, provided the transfer allows subsequentadsorption of the polymer in the more hydrophobic regions of thesubstrate surface. Using pre-patterned substrates the polymer patternsmay also be prepared by a layer by layer adsorption process through, forexample, electrostatic attraction or hydrogen bonding interactions.Furthermore, plasma patterning can be used for the same purpose.

Examples of suitable molecular “inks” include alkanethiols,organosilanes, and their derivatives, polyelectrolytes, H-bondingmolecules, etc.

In another embodiment of the invention the pattern is applied to thesubstrate using a micro-molding technique. This allows the formation ofa patterned polymer coating on the substrate through confined solventevaporation from a thin layer of polymer solution sandwiched between amold, such as an elastomeric mold, and the substrate surface. Theelastomeric mold may be made of any suitable material, such as PDMS,fluorocarbon or other solvent resistant elastomers. The mould surfacehas incised areas corresponding to the pattern desired which providechannels for the “ink”.

Once the polymer pattern is applied to the substrate, the patternedsubstrate is heated to a temperature at or above the temperature atwhich the polymer decomposes thereby forming a carbonised pattern on thesubstrate. In some circumstances it is desirable to heat the polymermaterial at one or more temperatures below the decomposition temperatureof the polymer material. Such heating can stabilise the polymer (e.g. bycross-linking etc.) such that the carbonised polymer pattern remainssubstantially intact during subsequent pyrolysis.

The next step in the process involves the synthesis of a layer ofaligned carbon nanotubes on the region of the substrate to which thecarbonised polymer is not attached. This may be achieved using asuitable technique for the synthesis of perpendicularly aligned carbonnanotubes. Preferably the aligned carbon nanotubes are prepared bypyrolysis of a carbon-containing material in the presence of a suitablecatalyst for nanotube formation.

The carbon-containing material may be any compound or substance whichincludes carbon and which is capable for forming carbon nanotubes whensubjected to pyrolysis in the presence of a suitable catalyst. Examplesof suitable carbon-containing materials include alkanes, alkenes,alkynes or aromatic hydrocarbons and their derivatives, for exampleorganometallic compounds of transition metals, for example methane,acetylene, benzene, transition metal phthalocyanines, such as Fe(II)phthalocyanine, and metallocenes such as ferrocene and nickeldicyclopentadiene and any other suitable evaporable metal complex.

The catalyst may be any compound, element or substance suitable forcatalysing the conversion of a carbon-containing material to alignedcarbon nanotubes under pyrolytic conditions. The catalyst may be atransition metal, such as Fe, Co, Al, Ni, Mn, Pd, Cr or alloys thereofin any suitable oxidation state.

The catalyst may be incorporated into the substrate or may be includedin the carbon-containing material. Examples of carbon-containingmaterials which include a transition metal catalyst are Fe(II)phthalocyanine, Ni(II) phthalocyanine and ferrocene. When the catalystand carbon-containing material are included in the same material it maybe necessary to provide sources of additional catalyst or additionalcarbon-containing material. For example, when ferrocene is used as thecatalyst and a source of carbon, it is necessary to provide anadditional carbon source, such as ethylene, to obtain the requirednanotube growth.

The pyrolysis condition employed will depend on the type ofcarbon-containing material employed and the type of catalyst, as well asthe length and density of the nanotubes required. In this regard it ispossible to vary the pyrolysis conditions, such as the temperature,time, pressure or flow rate through the pyrolysis reactor, to obtainnanotubes having different characteristics.

For example, performing the pyrolysis at a higher temperature mayproduce nanotubes having different base-end structures relative to thoseprepared at a lower temperature. The pyrolysis will generally beperformed within a temperature range of 500° C. to 1100° C. Similarlylowering the flow rate through a flow-type pyrolysis reactor may resultin a smaller packing density of the nanotubes and vice versa. A personskilled in the art would be able to select and control the conditions ofpyrolysis to obtain nanotubes having the desired characteristics.

After synthesis of the layer of aligned carbon nanotubes in thepatterned array on the substrate, the carbonised polymer remaining onthe substrate may be dissociated from the carbon nanotubes. This may beachieved by plasma etching. Alternatively it is possible to disassociatethe carbon nanotubes from the substrate by transferring the patternedcarbon nanotube layer to another substrate. This other substrate may beanother substrate capable of supporting carbon nanotube growth, or maybe a metal, metal oxide, semi-conductor material or a polymer. Examplesof suitable polymers include adhesive coated polymers such as cellulosetape, conjugated (conducting) polymers, temperature/pressure responsivepolymers, bioactive polymers and engineering resins.

Where the patterned layer of aligned carbon nanotubes is transferred toanother substrate which is capable of supporting carbon nanotube growth,it is possible to form a hetero-structured nanotube film by subjectingthe nanotube coated substrate to conditions for promoting aligned carbonnanotube growth. The conditions of nanotube formation may be controlledor adjusted such that the length of the further nanotubes is differentto the length of the nanotubes making up the original patterned layer.This second layer of nanotubes will tend to grow in the spaces definedby the original patterned layer. It may also be possible to adjustconditions such that there is some further nanotube growth on top of theoriginal patterned layer.

The nanotube patterns on quartz plates may also be separated from thesubstrate, while retaining the integrity of the pattern by immersing thesample in an aqueous hydrofluoric acid solution (10-40% w/w) for anappropriate period.

For some applications, the patterned carbon nanotube film may beincorporated into a multilayer structure including layers of othermaterials, such as metals, metal oxides, semiconductor materials orpolymers.

The patterned carbon nanotube film prepared in accordance with thepresent invention and the devices including these patterned filmsrepresent further aspect of the present invention.

The patterned film prepared in accordance with any one of the processesof the present invention and devices, materials coated with or includingthese multilayer films represent further aspects of the presentinvention.

As is evident from the above description the invention allows thepreparation of a large variety of patterned films and structures. Theprocesses of the present invention and the patterned structures formedmay have use in the following applications:

-   1) electron emitters-   2) field-emission transistors-   3) photovoltaic cells and light emitting diodes with region-specific    characteristics, and electrodes therefore-   4) optoelectronic elements-   5) bismuth actuators-   7) chemical and biological sensors with region-specific    characteristics-   8) gas storages-   9) molecular-filtration membranes-   10) region-specific energy absorbing materials-   11) flexible optoelectronic devices.

The invention will now be described with reference to the followingexamples and drawings which illustrate some preferred embodiments of theinvention. However it should be understood that the particularity of thefollowing description is not to supersede the generality of theinvention previously described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a pyrolysis flow reactorsuitable for preparing aligned carbon nanotubes.

FIG. 2 a is a schematic diagram showing the stages involved in thepreparation of a patterned layer of aligned carbon nanotubes accordingto a micro-contact printing process.

FIG. 2 b is a schematic diagram showing the stages involved in thepreparation of a patterned layer of aligned carbon nanotubes accordingto a micro-molding technique.

FIG. 3 a is a scanning electron microscopic image of patternedoctadecylsiloxane self assembling monolayers on quartz glass plates. Theblack and white lines represent SiO₂ and SAM respectively.

FIG. 3 b is a scanning electron microscopic image of a pattern ofDNQ-novolak photoresist selectively adsorbed in the OTS-free regions ofthe plate of FIG. 2A.

FIG. 3 c is a scanning electron microscopic image of carbon-surroundedFe particles selectively diffused in the polymer-free regions.

FIG. 3 d is an EDX profile of C and Fe. The scanning path for the EDSanalysers is indicated by the line between points A and B.

FIG. 3 e is a scanning electron microscopic image of a pattern ofaligned carbon nanotubes prepared using a micro-contact printingtechnique.

FIG. 3 f is a high magnification image of the aligned carbon nanotubepattern of FIG. 3 e.

FIG. 4 a is an optional microscopic image of the patterned surface of aPDMS mold.

FIG. 4 b is a scanning electron microscope image of the DNQ-novolakphotoresist pattern preparing using a micro-molding technique with thestamp of FIG. 3 a.

FIG. 4 c is a scanning electron microscopic image of aligned carbonnanotube patterns prepared from the prepatterned substrate of FIG. 4 b.

FIG. 4 d is a higher magnification image of the pattern shown in FIG. 4c.

DETAILED DESCRIPTION OF THE INVENTION Example 1

Quartz glass plates were cleaned by heating in a Pianha solution (amixture of 98% H₂SO₄ and 30% H₂O₂ at 7:3 v/v) at 70° C. for ca. 30 min,followed by thoroughly rinsing with deionized water. PDMS stamp was usedfor patterning an octadecyltrichlorosiloxane (OST) SAM layer on thecleaned quartz surface. After the contact transfer of the “ink” (i.e.0.2% w/w of OST in hexane), the PDMS stamp was left in contact with thesubstrate for 15-30 seconds, and the patterned substrate was thenimmersed into a diazonaphthoquinone (DNQ)-modified cresol novolakphotoresist solution (0.5˜1.0 mg/ml) in ethoxyethyl acetate/acetone(1/10˜1/5 v/v) for ca. Is for selective absorption of the polymer intothe OST-free regions. The polymer prepatterned quartz plate was heatedat high temperature under Ar atmosphere to carbonize the photoresistpolymer into a carbon layer. The carbonization was carried out beheating the patterned DNQ-novolak photoresist coating at 150° C., 300°C., 500° C., 700° C. and 900° C. for 30 minutes at each temperature.Carbonization of certain polymers has previously been reported (see, forexample: (a) Kyotani, T.; Nagai, T.; Inoue, S.; Tomita, A. Chem. Mater.1997, 9,609. (b) Parthasarathy, R. V.; Phani, K. L. N.; Marin, C. R.Adv. Mater. 1995, 7, 896). The carbon nanotube patterns were thenprepared by selectively growing aligned nanotubes in thephotoresist-free regions by pyrolysis of FePc under Ar/H₂ at 800-1000°C.

FIGS. 2 a & b represent typical scanning electron microscopic (SEM,XL-30 FEG SEM, Philips) images of patterned octadecylsiloxane SAMs onquartz glass plates and patterns of DNQ-novolak photoresistselectively-absorbed in the OTS-free regions. As can be seen, thepatterned structures shown in FIGS. 2 a & b are perfectly matched toeach other with the photoresist lines interdispersed between the OTSlines in FIG. 2 b. Upon heating the prepatterned quartz plate associatedwith FIG. 2 b at high temperatures under Ar atmosphere, the DNQ-novolakphotoresist layer was found to be carbonized into carbon black andremained on the quartz substrate while OTS molecules decomposed awayfrom the surface. Carbonization of the photoresist polymer was, mostprobably, due to the crosslinking effect of sulfate species originatedfrom the decomposition of o-diaxonaphoquinone groups, as the X-rayphotoelectron spectroscopic (XPS, Kratos Analytical, monochromatized AlKα at 200W) and energy dispersive X-ray (EDX) analyses on the carbonizedlayer indicated the presence of carbon with a trace amount of sulfate.FIG. 2 c, together with the associated EDX profiles of C and Fe given inFIG. 2d, clearly shows that the carbon-surrounded Fe particles forme atthe initial stage of the pyrolysis of FePc preferentially deposited inthe regions uncovered by the carbonized polymer pattern, presumablycaused by a localized surface energy effect associated with theprepatterned substrate. Further pyrolyzing FePc under Ar/H₂ at 800-1000°C., therefore, led to region-specific growth of aligned nanotubes in thepolymer-free regions as the presence of metal catalysts is known to bemandatory for the nucleation and growth of carbon nanotubes by pyrolysisof FePc. FIG. 2 e represents a typical SEM image for the alignednanotube micropatterns thus prepared. The width of the aligned nanotubearrays in FIG. 2 e is seen to be ca. 0.8 μm, which is almost the samevalue as that for OTS lines seen in FIGS. 2 a & b. Inspection of FIG. 2e at a higher magnification (FIG. 2 f) shows that the aligned nanotubesare densely packed along the line length, but only a few of thenanotubes were observed across the line width in some of the nanotubelines.

Example 2

A drop of the DNQ-novolak photoresist in the ethoxyethyl acetate/acetone(15˜20% w/w) was spread on a quartz plate, and PDMS stamp was thenpressed on the polymer coated quartz surface. After having dried in anoven at 80-100° C. for about 30 min, the PDMS stamp was removed leadingto a polymer-patterned substrate. The polymer prepatterned quartz platewas heated at high temperature under Ar atmosphere to carbonize thephotoresist polymer into a carbon layer. The carbon nanotube patternswere then prepared by selectively growing aligned nanotubes in thephotoresist-free regions by pyrolysis of FePc under Ar/H₂ at 800-1000°C.

DNQ-novolak photoresist patterns were prepared by the solvent-assistedmicro-molding (SAMIM) method illustrated in FIG. 1 b. The structure ofthe PDMS mold used in this study is shown in FIG. 3 a, while thecorresponding SEM image of the resulting photoresist pattern is given inFIG. 3 b. Prior to the region-specific growth of aligned nanotubes bypyrolysis of FePc under Ar/H₂ at 800-1000° C., the polymer patternedquartz plate was carbonized at high temperatures under Ar atmosphere asis the case with the micro-contact printing approach. FIGS. 3 c & d showtypical SEM images for the aligned nanotube patterns thus prepared.Unlike the micro-contact printing patterning, however, the micro-moldingtechnique eliminates the SAM pattern formation and selective adsorptionof DNQ-novolak photoresist chains involved in the micro-contact printingmethod, and hence serves as a more convenient approach for fabricatingmicro-/nano-patterns of the aligned nanotubes.

The present invention demonstrates the use of soft-lithographictechniques, including micro-contact printing and micro-molding, forfabricating patterned, perpendicular-aligned carbon nanotube arrays. Thealigned nanotube patterns thus prepared could have resolutions down tosub-micrometer scale. These facile methods for generatingmicro-/nano-patterns of aligned nanotubes suitable for devicefabrication could open avenues for fabricating various nanodevices for awide range of potential applications ranging from novel electronemitters in flat panel displays (de Heer, W. A.; Bonard, J.-M.; Fauth,K.; Châtelain, A.; Forró, L; Ugarte, D. Adv. Mater. 1997, 9, 87) toartificial muscles (Baughman, R. H.; Changxing, C.; Zakhidov, A. A.;Iqbal, Z.; Barisci, J. N.; Spinks, G. M.; Wallace, G. G.; Mazzoldi, A.;de Rossi, D.; Rinzier, A. G.; Jaschinski, O.; Roth, S.; Kertesz, M.Science 1999, 284, 1340.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The invention alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification, individually or collectively, andany and all combinations of any two or more of said steps or features.

1. A process for preparing a patterned layer of aligned carbon nanotubeson a substrate including: applying a pattern of polymeric material tothe surface of a substrate capable of supporting nanotube growth using asoft-lithographic technique; subjecting said polymeric material tocarbonization to form a patterned layer of carbonized polymer on thesurface of the substrate; and synthesising a layer of aligned carbonnanotubes on regions of said substrate to which carbonised polymer isnot attached to provide a patterned layer of aligned carbon nanotubes onsaid substrate.
 2. A process according to claim 1 wherein the polymericmaterial is a photoresist or photoresponsive material.
 3. The processaccording to claim 2 wherein the polymeric material is (DNQ)-modifiedcresol novolac resin.
 4. A process according to claim 1 wherein thepolymeric material is selected from the group consisting of epoxyresins, PEO, polyanilines, polymethyl methacrylate, polystyrenes,polydienes, and plasma polymers derived from saturated or unsaturatedalcohols, ketones, aldehydes, amines or amides.
 5. A process accordingto claim 1 where the substrate is a glass.
 6. A process according toclaim 1 wherein the substrate is selected from the group consisting ofquartz glass, graphite, mica, mesaporous silica, silicon wafer,nanoporous alumina and ceramic plates.
 7. The process according to claim6 wherein the substrate is quartz glass or silicon wafer.
 8. The processaccording to claim 1 wherein the substrate comprises a coating of amaterial which is capable of supporting carbon nanotube growth under theconditions employed.
 9. The process according to claim 8 wherein thecoating is selected from the group consisting of a metal, and metalalloys and compounds thereof having conducting or semiconductingproperties.
 10. The process according to claim 9 wherein the coating isa metal selected from the group consisting of Au, Pt, Cu, Cr, Ni, Fe, Coand Pd.
 11. The process according to claim 9 wherein the coating is ametal compound or metal alloy compound selected from an oxide, acarbide, a nitride, a sulfide and a boride.
 12. The process according toclaim 11 wherein the coating is a metal oxide selected from the groupconsisting of indium tin oxide (ITO), Al₂O₃, TiO₂ and MgO.
 13. Theprocess according to claim 9 wherein the coating is a semiconductingmaterial selected from the group consisting of gallium arsenide,aluminium arsenide, aluminium sulphide and gallium sulphide.
 14. Aprocess according to claim 1 wherein the soft lithographic technique isa microcontact printing technique.
 15. A process according to claim 14wherein self-assembling monolayers (SAMS) of a molecular ink is appliedto the surface of said substrate in a region specific manner, followedby adsorption of said polymeric material in the SAM-free regions.
 16. Aprocess according to claim 15 wherein the molecular ink is analkylsiloxane.
 17. A process according to claim 15 wherein the molecularink is applied using a stamp.
 18. A process according to claim 14wherein the hydrophobicity and hydrophilicity of the surface of saidsubstrate is altered by the region specific transfer to the surface ofthe substrate of a material which alters the hydrophobicity orhydropbiliclty of the surface, followed by the adsorption of the polymerin the more hydrophobic regions of the substrate surface.
 19. A processaccording to claim 1 wherein the soft lithographic technique is amicromolding technique.
 20. A process according to claim 19 wherein themicromolding technique comprises applying a thin layer of a solution ofsaid polymeric material in a solvent to said substrate surface,sandwiching the solution between said substrate surface and a moldsurface, said mold surface having incised areas corresponding to thepattern to be formed on the substrate surface, allowing the solvent toevaporate and removing the mold to provide a pattern of polymericmaterial on the substrate surface.
 21. A process according to claim 20wherein the mold is composed of PDMS, fluorocarbon or other solventresistant elastomers.
 22. A process according to claim 1 wherein thepolymeric material is carbonized by heating to a temperature at or abovea temperature at which said polymeric material decomposes.
 23. Theprocess according to claim 1 wherein the aligned carbon nanotubes aresynthesised by pyrolysis of a carbon-containing material in the presenceof a suitable catalyst for nanotube formation.
 24. The process accordingto claim 23 wherein the carbon-containing material is selected from thegroup consisting of alkanes, alkenes, alkynes and aromatic hydrocarbonsand derivatives thereof, organometailic compounds of transition metalsand other suitable evaporable metal complexes.
 25. The process accordingto claim 24 wherein the carbon-containing material is selected from thegroup consisting of methane, acetylene and benzene.
 26. The processaccording to claim 24 wherein the organometallic compound is atransition metal phthalocyanine.
 27. The process according to claim 24wherein the organometallic compound is a metallocene.
 28. The processaccording to claim 23 wherein the catalyst is a transition metal. 29.The process according to claim 28 wherein the transition metal isselected from the group consisting of Fe, Co, Al, Ni, Mn, Pd, Cr andalloys thereof in any suitable oxidation state.
 30. The processaccording to claim 23 wherein the catalyst is incorporated in thecarbon-containing material.
 31. The process according to claim 30wherein the catalyst is selected from the group consisting of Fe(II)phthalocyanine, Ni(II) phthalocyanine and ferrocene.
 32. The processaccording to claim 30 further comprising an additional source ofcatalyst.
 33. The process according to claim 30 further comprising anadditional source of carbon-containing material.
 34. The processaccording to claim 23 wherein the pyrolysis is carried out at 500° C. to1100° C.
 35. The process according to claim 1 wherein the processcomprises a further step of dissociating the aligned carbon nanotubesfrom the substrate.
 36. The process according to claim 35 wherein thesubstrate is quartz glass and dissociation is effected by immersing thesample in an aqueous hydrofluoric acid solution (10-40% w/w).
 37. Theprocess according to claim 35 wherein dissociation comprisestransferring he patterned carbon nanotube layer to another substrate.38. The process according to claim 37 wherein the other substrate iselected from the group consisting of another substrate capable ofsupporting carbon nanotube growth, a metal, a metal oxide, asemiconductor material and a polymer.
 39. The process according to claim38 wherein the polymer is selected from the group consisting of adhesivecoated polymers, conjugated (conducting) polymers, temperature/pressureresponsive polymers, bioactive polymers and engineering resins.
 40. Theprocess according to claim 39 wherein the adhesive coated polymer iscellulose.